Flyfish2002, First, consider that the KT120 has only just recently hit the market. Other than its rating there is little to substantiate a recommendation for 'reliability'. But, the spec's are impressive and I can understand why Chris would recommend them as an alternative.
FWIW, I have some SFM's in my attic which I purchased used. The previous owner had problems with tubes in it (he was using KT88's not know for stability) and gave up out of frustration. I used SED 6550's - had no problems until I plugged in a 'rugged' KT88 and one went and took out a cathode resistor. I had it repaired and recapped - after which I lost one of my SED 6550's in one. Now they just sits in the 'attic' - I need neither the power nor the hassle of hauling it to the techie.
I'm not dis'ing these amps, they sound fine, its just that they were designed around a very rugged tube (EI KT99), which haven't been available for a long time, that could handle the very high plate voltage of these amps (650 as I recall - read your manual for exact specs).
FWIW.
FWIW, I have some SFM's in my attic which I purchased used. The previous owner had problems with tubes in it (he was using KT88's not know for stability) and gave up out of frustration. I used SED 6550's - had no problems until I plugged in a 'rugged' KT88 and one went and took out a cathode resistor. I had it repaired and recapped - after which I lost one of my SED 6550's in one. Now they just sits in the 'attic' - I need neither the power nor the hassle of hauling it to the techie.
I'm not dis'ing these amps, they sound fine, its just that they were designed around a very rugged tube (EI KT99), which haven't been available for a long time, that could handle the very high plate voltage of these amps (650 as I recall - read your manual for exact specs).
FWIW.